The number of shops selling marijuana has exploded from 186 two years ago. Officials hope to impose some order by capping the number of outlets or by requiring a certain distance between stores.

For a moment two years ago, Los Angeles officials thought they knew how many marijuana dispensaries the city had: 186. That's how many registered to operate under the city's moratorium. The city quickly lost control, and the number soared: 500, 600, 800, now perhaps 1,000.

On Tuesday, the City Council will grapple with a question it has barely debated since the number started to rise: How many is too many?

Councilman Jose Huizar, whose district includes Eagle Rock, one of the first neighborhoods to recoil from the influx of dispensaries, has suggested a cap of 70. The proposal is one of more than three dozen amendments the council will weigh when it resumes debate on its proposed medical marijuana ordinance.

"Since this is a new frontier for the city to engage in, we want to make sure that we can do everything that's possible to monitor them," Huizar said. "We've got to take this in incremental steps, and I'd rather start with a low number."

The city attorney and L.A. County district attorney vigorously oppose the sale of medical marijuana at dispensaries, saying it violates state law, and have asked the council to ban it. But council members appear inclined to disregard their advice.

Cities have limited the number of dispensaries in two ways. The most common is to require them to be a certain distance from places that children frequent, such as schools and libraries. That's the approach in the proposed city ordinance. Less common, but gaining in popularity, is a cap on the number of shops.

Officials in cities with caps -- including Oakland, Berkeley, West Hollywood and Sebastopol -- say caps allow them to select responsible operators, keep a close eye on them and shut them down more easily if they become a nuisance.

"I can't imagine trying to monitor 800," said Larry Robinson, a councilman in Sebastopol, a small city in Sonoma County that allows two, although only one has opened. Peace in Medicine has been in business more than two years. It is so well-run that Police Chief Jeffrey Weaver said, "We have more calls at a Taco Bell."

But medical marijuana advocates caution that an arbitrary cap could limit access. "The problem with Los Angeles is that it is so different from any other city in the state in terms of its geographical size and population that I'm not sure a cap makes any sense," said Kris Hermes, a spokesman for Americans for Safe Access, an advocacy group that promotes the use of medical marijuana.

The over-concentration of dispensaries, as Huizar calls it, is what spurred the council this summer to move forward.

Shops continue to open with no public input and almost no city oversight, irritating activists and business owners who complain they bring crime, parking problems and patrons who light up in neighborhoods.

In Eagle Rock, CQPR Collective is sprucing up a store on Colorado Boulevard and may open this week across from House of Kush, which the council voted to close in June. A stretch of Pico Boulevard is celebrated on pot websites as the Green Mile.

On Melrose Avenue between Fairfax and Highland avenues, 13 dispensaries opened this year. In Woodland Hills, Ventura Boulevard has so many that a resident compared the traffic to a drive-through line at In-N-Out.

The proposed Los Angeles ordinance would initially cap the number at the original 186 by requiring other dispensaries to close for six months before applying to reopen.

It also requires dispensaries to be 1,000 feet from each other, schools and other institutions. That would also reduce the number, but city officials are not sure by how much. A study of the 186 concluded that about three-quarters of them would have to move or close.

That has led some council members to suggest a 500-foot setback, but no studies have been done to show how many dispensaries that would allow.

Michael Larsen, the public safety director of the Eagle Rock Neighborhood Council, supports Huizar's proposal. "I would like to know that we aren't going to be constantly looking at the next new collective to come in," he said.

But Michael Backes, who runs Cornerstone Research Collective on Eagle Rock Boulevard, worries that a cap would force him out of business, even though he registered with the city under the moratorium.

"I would say the odds are pretty good that we won't survive," he said. "Going through the city planning process is usually pretty expensive, and we operate as a nonprofit."

The cities with caps are smaller and more compact than Los Angeles, which has more than 4 million people spread out over about 470 square miles. Berkeley, with a population of 107,000, allows three shops; Palm Springs (population 47,600), two; West Hollywood (population 37,000), four; and Sebastopol (population 7,700), two. Oakland, with a population of 425,000, has four, which split about $20 million a year in pot sales.